Bispecific antibodies have emerged as a promising cancer treatment, with a growing list of encouraging clinical results. For example, blinatumomab, a murine anti-human CD3 x anti-human CD19 bispecific antibody has produced clinical remission in precursor B cell acute lymphoblastic leukemia (B-ALL) patients at thousands times lower dosage than conventional antibody therapies, such as rituximab (anti-human CD20).[1] These findings have spurred a great deal of interest and growth in the field, with particular attention being focused on developing new methodologies to generate bispecific antibodies (e.g. Triomabs, BiTEs, Dock and Lock, etc.) in high yields and purity. Despite continual progress, all current bispecific antibody technologies still require a tremendous amount of antibody engineering and cloning upfront to generate even a single functional product, which can be time consuming and challenging. Technologies utilzing scFv's are also faced with concerns over functionality, solubility, stability, avidity, and pharmacokinetics. Addin to the challenges in producing bispecific antibodies is an incomplete understanding of their modes of action. For example, not all anti-CD3 antibodies work equally well to trigger T-cell activation. Given these uncertainties and the high cost and time required for production, a methodology that allows bispecific antibodies to be rapidly produced without the need for antibody engineering and cloning would be cost-effective, significantly increase throughput, and ultimately lead to a deeper understanding of the underlying biological mechanisms that lead to improved therapeutic efficacy. We therefore propose to develop a facile method for the efficient production of bispecific antibodies from full- length unmodified IgG, without the need for antibody engineering, cloning, or modifications. The bispecific antibodies will be produced with high purity in as little as one day. Several benefits of working with intact IgG are that they are stable, can be produced in high yield, offer high-avidity bivalent binding, and are expected to maintain Fc-effector functions, including antibody dependent cell-mediated cytoxicity (ADCC) and complement- dependent cytotoxicity (CDC). The specific aims for the proposal are (1) Optimize procedure for preparing bispecific antibodies from full-length, unmodified IgG; (2) Evaluate the functionality and efficacy of anti-CD20 x anti-CD3 bispecific antibodies in vitro; (3) Determine the pharmacokinetics and efficacy of CD20 x CD3 bispecific antibody in vivo.